Better handling with state change callback

[d-a-v]

Call our own netif_status_changed from netif->status_callback() as it should have been from the beginning.

Using esp8266/Arduino mDNS example, where

• AP is started first
• mDNS is started
• STA is started later

Without this change, status callback is called only for STA, once, when IP address is not assigned
With this change, status callback is called when AP or STA change their state, including when an IP address is later set by DHCP.

[mcspr]

Yep, makes sense.

So the idea with hiding original (sdk) callback is only make status work with our objects?
From Arduino side, I assume we already know that status callback may also be called on flag down?
Minor nit... any reason for commenting out code instead of relying on vcs history?